Charles' correspondence with ministers - known as "black spider" memos - will be released following a long-running battle by Guardian newspaper journalist Rob Evans to see the documents following a freedom of information request.

The letters will be published with some redactions following the Upper Tribunal's ruling yesterday that it "has accepted Mr Evans's submission that what is described in the decision as 'the open material' is to be supplied to other parties without restriction on their ability to publish that material".

The decision of the tribunal included a proviso that the material could be published subject to any "provisional redactions" to protect personal data of people other than Charles.

Supreme Court judges finally approved the publication of the letters in March.

The Prince's notes were sent to a number of Government departments and written between September 2004 and March 2005.

They reflect, according to previous attorney general Dominic Grieve, Charles' "most deeply held personal views and beliefs''.

They are known as "black spider" memos because of his distinctive handwriting and abundant use of underlining and exclamation marks.

Mr Grieve vetoed an original decision to order publication made by the Upper Tribunal in 2012, but it was eventually ruled that his actions were invalid, paving the way for the documents finally to be disclosed.

The documents are expected to be published by the Guardian, the Information Commissioner and the Cabinet Office at 3pm.